I want a double layered material, with the outer layer being glass, how can I achive that?
Viewing-Angle Based Solution
This setup works well for curvy objects.

But on a cube, for example, it is far less convincing.

I'm sure that with some serious noding you could get much closer, but it may not be worth the effort.

Node Explanation
Inner Material
The Diffuse BSDF node is the plug'n'play part of the node tree. Whatever shader is put in its place will look like it is coated in glass.
The normals of this part are slightly warped by the Reflection coordinates to approximate the refraction of the glass coating.

Glass Mix Factor
This part creates a mask at grazing viewing angles that is either black or white.
To keep the glass bright, all back faces are added to the mask. If this is not done, the glass will often look dark.

Clearcoat Mix Factor
Once the glass has been mixed in, there is no reflection above the inner material. To add this only where the glass is not already part of the shader, subtract the glass' mix factor from the Fresnel (which should have the same IOR as the Glass BSDF).